Simultaneous formation of expanding borax particles and spray dried detergents

ABSTRACT

Hydrated borax, such as Na2E4O7.5H2O, is expanded to a product of low density by passing individual particles downwardly through a relatively slow-moving countercurrent hot air stream in which the particles are heated by convection and by radiation from internal walls of a confining structure. The expanded and dehydrated borax particles resulting are of a bulk density about half or less than that of the density of the original particles. In a preferred embodiment of the invention, a detergent composition less borax is sprayed into the top of a countercurrent spray tower and at a point below the spray inlet, where the produced detergent composition particles are virtually dry, borax pentahydrate is fed into the tower and is dehydrated, expanded and intimately mixed with the other spray dried particles to form a built detergent product containing desired low density borax. Since the densities of the products and particle sizes thereof may be controlled, non-stratifying built detergent can be made, in which the detergent and borax particles are of comparable size and density, or the bulk density of the overall product can be varied by controlling the degree of expansion of the borax.

United States Patent [191 Gibbons [451 May 6,1975

[54] SIMULTANEOUS FORMATION OF EXPANDING BORAX PARTICLES AND SPRAY DRIEDDETERGENTS Edward James Gibbons, Fanwood, NJ.

[73] Assignee: Colgate-Palmolive Company, New

York, NY.

22 Filed: Feb. 11, 1974 211 Appl. No.: 441,302

Related US. Application Data [62] Division of Ser. No. 885,079, Dec. 15,1969,

[75] Inventor:

Primary Examiner-Benjamin R. Padgett Assistant Examiner-Christine M.Nucker Attorney, Agent, or Firm-Herbert S. Sylvester; Murray M. Grill;Norman Blumenkopf [5 7] ABSTRACT Hydrated borax, such as Na E,O,-5H 0,is expanded to a product of low density by passing individual particlesdownwardly through a relatively slow-moving countercurrent hot airstream in which the particles are heated by convection and by radiationfrom internal walls of a confining structure. The expanded anddehydrated borax particles resulting are of a bulk density about half orless than that of the density of the original particles. In a preferredembodiment of the invention, a detergent composition less borax issprayed into the top of a countercurrent spray tower and at a pointbelow the spray inlet, where the produced detergent compositionparticles are virtually dry, borax pentahydrate is fed into the towerand is dehydrated, expanded and intimately mixed with the other spraydried particles to form a built detergent product containing desired lowdensity borax. Since the densities of the products and particle sizesthereof may be controlled, non-stratifying built detergent can be made,in which the detergent and borax particles are of comparable size anddensity, or the bulk density of the overall product can be varied bycontrolling the degree of expansion of the borax.

7 Claims, 2 Drawing Figures PATENTEUHAY 61975 FIG. 2

INVENTOR EDWARD J. GIBBONS ATTORNEY SIMULTANEOUS FORMATION OF EXPANDINGBORAX PARTICLES AND SPRAY DRIED DETERGENTS This is a divison ofapplication Ser. No. 885,079 filed Dec. l5, 1969, now abandoned.

As usually sold in commerce, borax is a solid hydrated particulatematerial. For some purposes it is desirable that it be employed in suchcondition but in other applications, the anhydrous particulate form orparticles of lower degrees of hydration are preferred, especially if arapid solubility is required.

It has been known that calcining or decrepitation of borax hydratesproduces an expanded particle, apparently due to the swelling action ofescaping water vapor. The property of expansion of the borax seems todepend on the heated crystals, while still containing water, being fluidenough to be enlarged and, at the same time, being strong enough not tocollapse upon cooling. Various methods have been suggested for effectingthe drying and puffing or decrepitation of borax hydrates, such as theuse of kilns, roasting pans and fluidized bed apparatuses, when solidborax crystals are being dehydrated, and spray towers for drying liquidsolutions or crutcher mixes of borax.

Borax has examples accepted as a desirable constituent of builtsynthetic organic detergent compositions. lt exerts a water softening Itand appears to improve detergency of compositions containing syntheticorganic detersive ingredients. lt retards the growth of fungi and helpsmake wash aesthetically more pleasing, as well as cleaner, causing itprinciples smell sweeter. Consequently, borax powders have been sold foraddition to washing solutions and borax detergent compositions have beenmade by blending borax particles with other detergents or by dryingfluid mixtures or pastes of borax and other detergents. Despite the needfor an improved way of preparing dehydrated borax of these uses, beforethe present invention it was not known to expand solid particles ofborax by dropping them through a relatively slowly upwardly risingheated gas so as to produce a final structurally stable borax product ofdesired dryness and low density. Nor was it known to decrepitate boraxin such manner in an operation undertaken in conjunction with thepreparation of other detergent product components.

The advantages of the invented process are many. Compared to prior artprocesses in which borax particles were entrained in a rapidly movingheated gas, which caused calcination, much less breakage of productresults and less heat is needed, thereby raising the efficiency of theprocess ad decreasing expense. Also, the present process lends itself touse in many standard spray drying towers, thereby not requiring specialapparatuses which cannot be made by rather simple modifications ofexisting equipment. In addition to economic and design advantages and tothe obtaining of a product in better physical form, the present methodalso allows the puffing of the borax to be used as a control of densityof the borax or a detergent incorporating borax particles. The gentledehydration of the borax particles allows one to dispense with the needfor complex dust collecting equipment, if the initial feed of boraxparticles contains no fines. lf fines are present, they may be removedfrom the borax feed initially, thereby saving the need for dustcollecting equipment on the drying apparatus, or they may be charged tothe dryer and any fine expanded particles resulting may be removed bydust collectors, which are already parts of conventional spray dryerinstallations. Of course, much of the fine material charged will be somuch expanded by the present process that the particles produced willnot be dusty.

Other advantages of the present process include allowing a single spraytower to be used for several types of products, those containing boraxor other calcinable materials and those containing none of these. Thus,in a detergent plant, borax may be puffed in the same spray tower inwhich other detergent ingredients are being spray dried. By varying thefeeds of borax to such a tower, the composition of the product can bechanged or its density can be desirably controlled. The injection of theborax solid below the point of spraying of other constituents of thedetergents increases the ca pacity of the crutchers and the dryingtower, because it is not necessary to mix the borax with the otherdetergent ingredients in the crutcher. Furthermore, the process lendsitself to the addition to detergent compositions of materials ofstability insufficient to allow them to be blended with otheringredients in a crutcher. As examples of such materials may bementioned sodium perborate and other oxygen-releasing compounds such assodium percarbonate, sodium peracetate and potassium persulfate.

By means of this decrepitation process, utilizing equipment already onsite in a detergent plant, different forms of borax may readily be madeavailable for incorporation in detergent products of different desiredcharacteristics. For example, where the highly hydrated form is wanted,no calcining will need to be effected but in fomulations where differentdegrees of hydration are required or where low density products aredesirable, the hydrated borax in stock may readily be changed to other,more acceptable, less hydrated forms for these particular uses. Thus, itis only necessary to purchase and stock the borax of the highest degreeof hydration desired and convert it to other forms, when needed.

ln accordance with the present invention, a method for expanding ahydrate or borax to produce a low density product comprises passingparticles of borax hydrate downwardly through a slow movingcountercurrent hot drying gas stream in a walled drying zone, so thatthe particles are heated by convection from the hot gas and by radiationfrom a wall of the zone, and are dehydrated, and removing from the zonedehydrated, puffed particles of low density. In a preferred embodimentof the invention, a particulate detergent composition is manufactured byspraying into an upper portion of a countercurrent spray tower or dryingzone a liquid mixture of detergent components, and feeding into thespray tower or drying zone, at a point below the spray inlet, and wherethe sprayed detergent composition is in a virtually dry particulateform, particles of borax hydrate or other calcinable and puffablematerial to heat, dehydrate, and expand the borax hydrate and intimatelyto mix it with the other spray dried particles of detergent composition,to form a built detergent prod uct containing low density borax, andremoving the built detergent product from the drying zone. In anotherembodiment of the invention, the rate of feed borax hydrate particles isvaried or the location of the point of feed is changed to adjust theproportion of puffed borax and the extent of puffing of such product inthe detergent composition, whereby the bulk density of the finaldetergent product containing borax is controllable to rigid densityspecifications.

The present invention, and the objects and advantages thereof will beunderstood by one of skill in the art from reference to the followingdescription and the accompanying schematic drawing, in which:

FIG. 1 is a schematic partial vertical central sectional elevation of anapparatus for calcining hydrated borax; and

FIG. 2 is a schematic partial vertical central sectional elevation of anapparatus employed to practice a pre ferred method of the presentinvention, wherein the detergent composition containing puffed borax isproduced, illustrating how final product density is controlled either byvarying the feed of borax hydrate or by changing the extent of hydrationof the borax.

In FIG. 1 a drying zone 11 in a tower 13 is heated by heater 15 on theexternal walls 17 of the tower, thereby conducting heat to the internalwalls from which it radiates onto material within the drying zone. Purgeair at a comparatively low temperature enters the drying zone at thebottom thereof through conduit 19 and passes through the drying zone andout exit conduit 21. During passage through the drying zone the purgeair increases in moisture content and temperature. At the top of thedrying zone is an inlet 23 through which borax hydrate 25 is dropped.During passage through the heated portion of and tower, the hydrate isreduced in moisture content and exits through outlet 24 as anhydrousborax or borax monohydrate, which drops into receptacle 29. The feed ofborax to the drying zone is from a hopper 31 through a worm feeder 33.The rate of feed of borax is controllable by varying the speed of adrive motor 35 operatively connected with worm feed mechanism 33. Thetemperature of the drying zone is controllable by increasing ordecreasing the amount of heat furnished to heaters 15 and regulating theflow of the purge air. Thus, the desired feed, air anad heating ratesmay be regulated to produce most economically the dried product wanted.By heating only the upper proportions of heater units 15, the dwell ofparticles in a heated zone can be diminished so as to decreasedehydration. Such dwell time can also be regulated by varying the speedof the purge air, the temperature of the heaters and the fineness of theborax hydrate feed crystals.

In FIG. 2 a detergent composition less borax, sodium perborate or otherhydrated solid material that it is desired to dehydrate, is prepared asan aqueous suspension or paste in a crutcher or other suitable mixer 41and is pumped via pump 43 and line 45 to spray head 47, from which it issprayed into the interior of a spray towr 49. tower falling through thetower the spray 51 is dried to solid particles 53 by hot air enteringthe tower at inlet 57 and exiting through outlet 59. The hot air isusually produced by burning either fuel oil or gas in a burner, notillustrated. Solid hydrated borax or other non-crutchable solid materialwhich can be dehydrated and expanded is fed by feeder means, such as theworm feeder 33, from hopper 61 through pipe 63 past valves 65 and 67 andthrough valve 69 into the drying zone 71 through inlet pipe 73. Anothervalve 75 and other inlets 77, 79 and 81 are provided to allow forfeeding borax pentahydrate to any of several desired levels in the spraytower. Instead of plurality pluarlity of the valves with a singlefeeder, a plurality of controllable feeders may be utilized to regulatethe rate and height of borax addition to the tower. Thus, the time ofdwell of the borax hydrate particles in a heated area can be controlledby controlling the height at which they are fed into the spray tower.This also allows it to be assured that the particles fed to the tower donot contact wet detergent composition being sprayed, in those instanceswhere it is important that the materials do not agglomerate. Of course,the degree of hydration of the borax can also be controlled by changingthe temperature of the hot air being fed into the spray tower butlowering this temperature too much will have an adverse affect on thedrying of the rest of the detergent composition.

The desired product, a blend of detergent composition and borax or othernon-crutchable dehydrated constituent, is removed at 83 and is droppedonto a weighing belt 85, which supports a given volume of material. Whenthe weight on the belt becomes excessive, indicating too high density ofproduct, an electrical contact is made which opens a valve 87, whichregulates the amount of feed of borax hydrate, in those instances wherethe dehydrated borax is lower in density than the detergent composition.Conversely, if the borax is heavier than the detergent composition, theexcess weight on the weighing belt 85 will decrease the rate of feed ofborax hydrate. Altenatively, when the belt indicates that product madeis too light, the weigh belt can actuate valves 65, 67, 69 and 75, so asto feed the borax hydrate into the tower at a lower point to diminishdehydration and puffing and to increase its density. Such a modificationhas the advantage of making a product with a constant proportion ofborax in it, rather than one in which the percentage of this buildersalt varies. Of course, controllable feeders may be used instead ofvalve controls, to regulate borax hydrate additions.

Through exit 59 go cooled and moist drying gas and any dust particles ofdetergent composition or borax fines. Usually, little borax will gothrough duct 59, unless the solid material is exceedingly fine. However,due to the particle size distribution obtained by spraying crutchermixes through fine orifices, which include many fine particles, dustcollectors, not shown, will ordinarily be employed in communication withexit 59 to avoid discharging fine detergent powder into the atomsphere.

In carrying out the puffing of borax hydrate particles to convert themto the anhydrous or monohydrate form, as desired, the particle sizes ofthe borax fed to a decrepitation tower are those suitable for theparticlar operation and use. As a general guide, applicable to mostcommercial detergent products on the retail market, the particle sizeresulting should be such that the expanded borax will pass through a 6mesh sieve and over or substantially all will not pass through a 200mesh sieve. Preferably, the particles will pass through an 8 mesh sieveand be deposited on a 140 mesh sieve. Most preferably, the particleswill be within the 20 to mesh sieve range. Because the expandedparticles are larger than those of the hydrate charged, thecorresponding ranges for the borax hydrate to be expanded are adjusteddownwardly, accordingly. Thus, the particles charged will usually bewithin the range of 20 to 200 mesh, perferably from 40 to 180 mesh andmost preferably from 40 to mesh.

The extent of puffing may be adjusted by control of the temperature inthe zone where the expansion takes place and by the dwell of theparticles in that zone, for particles of given sizes. Also it is evidentthat faster expansion or greater relative puffing will be obtained withsmaller particles than those of larger sizes, if the same temperatureand time conditions prevail. Keeping in mind that such adjustments ofconditions will be made to obtain the desired results, nevertheless,general ranges of such conditions may be given, which will produceparticles of bulk density from about 0.1 to 0.8 times the bulk densityof the borax hydrate charged, which will be 0.1 to 0.6 g./cc. The dwellof particles in a heated zone where they are being decrepitated willusually be for a period of time from as little as 0.1 to seconds, on theaverage, although it is preferred to maintain this time as short aspossible, so as to effect a most efficient operation and obtainspeediest throughput. The preferred dwell is form 0.2 to 5 seconds andmost preferably, from 0.2 to 3 seconds. In such time, the particle willbe inserted into the hot drying zone and will have fallen through it toa relatively cool collecting zone. To obtain the monohydrate or morehighly hydrated form of the borax charged, one will usually hold thedwell in the heated zone to the lower portions of the ranges given andmight begin with a more highly hydrated form of borax, such as the boraxdecahydrate. Conversely, when an anhydrous product is desired, thedecrepitation time will normally be increased to the higher limits ofthe time ranges given and, if desired, the borax particles charged maybe the lower hydrates.

The decrepitation zone will normally be operated under atmosphericpressure or at a very slight vacuum or pressure up to about 1 millimeterof mercury. At such conditions, the temperature of the gas in thedecrepitation zone, usually air, sometimes containing products of fuelcombustion, will be from about 120 to 600C, preferably from 140 to 300C.and most preferably from about 180 to 240C. At such temperatures, goodcontrol of puffing is obtainable and the particles resulting are usuallystructurally stronger than if other temperatures are employed.Furthermore, good production rates are obtainable. Unless the anhydrousform of the borax is desired, the dwell time of the particles in thedecrepitation zone will be short enough so that the temperature of theparticles themselves will not greatly exceed 100 of the C., at whichtemperature all the water of hydration will be removed. Of course, wherethere are particles of different sizes, it is possible that some of themmay be completely dehydrated and others will be only partiallydehydrated. It is recognized that although uniformity of hydration isdesirable and is substantially obtainable by the method of thisinvention, mixtures of particles having an average degree of hydrationwithin the range herein described are contemplated.

The internal temperature of the decrepitation or drying zone is obtainedby regulation of the heat supplied, zone size, rate of feed of materialto be dehydrated, its initial degreee of hydration, and passage of gasthrough the zone. The heat may be supplied by an external heatingdevice, such as that illustrated in FIG. 1, whereby the zone wallsradiate heat onto the particles and allow convection currents to carryheat from the walls to gas adjacent to the drying particles. If such atechnique is applied, the zone wall should normally be heated to withinthe range of to 400C, preferably from 300 to 350C. The diameter of thezone will usually be from as little as 3 inches for laboratory and pilotplant equipment, to as much as 30 feet for production apparatuses.Usually, drying towers will have diameters of from 8 to 20 feet. Ofcourse, the heat supplied to the walls of the drying zone will have tobe at a sufficiently high temperature so that the radiation andconvection resulting are sufficient to raise the temperatures of theparicles to be decrepitated to the levels indicated previously. Toassist in the transfer of heat by convection, and to remove water fromthe decrepitation zone, it is usually desirable to employ a purge gas,which may be air, products of combustion or other suitable dry gas. Suchgas will normally pass through the drying zone in an upward direction ata rate of from 0.05 to 5 feet per second, preferably from 0.1 to 2 feetper second. By regulation of the flow of this gas it is possible tocontrol the dwell time of the borax particles to an extent.

if, instead of a heated wall of the drying zone, a heated drying gas isemployed, use of a purging gas is unnecessary, although it may beemployed and proportions thereof may be controlled, with respect to thedrying gas used, to regulate the temperature of the zone. To an extent,such regulation will also control the speed of free fall of theparticles. The temperature of the drying gas or the mixture of dryinggas and diluting gas, if such is employed, should be held within theranges given previously for the interior temperature of the drying zone.

As was mentioned previously, it is desired to maintain the boraxparticles in the puffing Zone for a comparatively short period of time.By employing high speed gas flow upwardly through the drying zone, thetendency would be for fines to be carried upwardly and out of the towerand for other particles to be held suspended, with the speed of the gasacting to a significant extent to nullify the forces of gravity. In thepresent invention wherein short dwell time in the decrepitation zone isdesired, the upward flow of gas is at a comparatively slow rate, so thatthe force of gravity is largely determinative of the dwell of particlesin the active dehydrating zone. Thus, the speed of the drying gas, whichwill usually be within the range of 0.05 to 5 feet per second andpreferably less than 1 or 2 feet per second, has little effect on thefree fall of the borax particles and allows rapid movement thereofthrough the dehydrating zone.

Tl-le relatively short stay of the borax particles in the dehydratingzone is important in maintaining the integrity of the particles becauseit limits the number of contacts these relatively fragile materials withother particles in the dehydrating zone. It also prevents much contactwith the walls of the zone. Therefore, the product resulting is ineffect, merely an enlarged form of that which was charged to thedecrepitation zone and includes very little fine material. Even if finesare initially charged, they are enlarged by the decrepitation processand may become substantially unobjectionable. If some fines areproduced, either due to initial charging of fines or to drying of othermaterials in the dehydrating zone, these may be removed in the exit gasby usual means, such as dust collectors, cyclone separators, spraywashes or other suitable apparatuses.

THe practice of the invention is trouble-free and subject to simplecontrols to modify the characteristics of the product desired. Thus, asis illustrated in H6. 2,

which shows a preferred modification of the invention, the feed of theborax hydrate may be varied and the height at which it is fed into thetower or dehydrating zone may be changed, so as to obtain differentdehydrating effects. Such changes may be controlled manually or byautomatic equipment response to the density or other characteristics ofthe product made. The decrepitation method is highly efficient,inexpensive, readily controllable and produces an excellent product,which does not have to be further dried or modified to acquire desiredpreperties. The method lends itself to other modifications which make ituseful in conjunction with ordinary spray drying processes. For example,in many detergent products it is desirable to include compounds whichare not sufi'lciently heat-stable to permit ordinary spray drying. Suchmaterials, for example, sodium perborate, organic dyes or desired bydrates, can be sprayed into the decrepitation zone together with thesolid borax particles and the decrepitating borax will furnish supportsfor the usually smaller quantities of the unstable material. Mixtures ofborax and perborate, for example, may then be blended in with otherordinary spray dried detergent components. in such operations, byutilizing different heights of spray nozzles or borax addition points,as illustrated in FIG. 2, the drying process can be modified so as toobtain the most efficient drying and the greatest stability of theperborate or other decomposable material.

In a preferred embodiment of the invention, as is illustrated in FIG. 2,a detergent composition, less borax and less unstable materials, such assodium perborate, is spray dried in a conventional countercurrent spraytower and below the dried particles the borax hydrate is added so thatthe decrepitation thereof occurs while the particles are falling, withthe spray dried particles, through a slowly rising hot air current. Theconditions employed, with respect to the borax particles are the same asthose previously described. So are the temperatures and air flow ratesin the lower portion of the drying zone, wherein decrepitation of theborax takes place. However, although it is usually desirable to employsimilar conditions throughout the entire drying zone, in some instancesit will be important to obtian higher temperatures to assist in dryingaqueous solution-suspensions of detergent, which usually include largerproportions of water than are found in the borax hydrates, or else areotherwise more difficult to dry. In such instances, additional dryinggas may be added to the drying zones above the borax inlets and thetemperature of the gas may be higher. In such cases temperatures of thedrying gas may be from 300 to 800C, although it is preferred to employtemperatures within the range of 500 to 600C. The spray nozzles employedand the spray pressures used are those known to the art, with thepressures normally being from 400 to 800 pounds per square inch,preferably from 500 to 700 pounds per square inch, and the particlesizes resulting from atomization being such as to produce particlesmostly within the range of 12 to 100 mesh, preferably 20 to 100 mesh. Ofcourse, some fines will be produced in spray drying because of thevariety of particle sizes in the sprays created. The fines are usuallycollected form the exit gas by a dust collector or other suitable means,after which they may be fed back into the system. An advantage of thedecrepitation of borax below the spray drying zone is in the curingwhich the release of small proportions of water in the decrepitationzone can exert on the dried detergent particles. The moisture content ofsuch particles may be raised slightly and the subjection of theparticles to the moisture at a relatively low temperature can assist inpartial hydration thereof and can counteract a tendency of some suchparticles to develop tackiness upon subsequent exposure to a humidatmosphere. The moisture content of the spray dried detergent containingborax will usually be from about 3 to 10%, with the borax particlesthemselves containing from about 0 to 10% water of hydration. Theproportion of borax in the detergent may be whatever is consideredsuitable for the intended purpose thereof but usually from 10 to 50%,preferably from 15 to 30% will be employed.

The detergent component of the spray dried material will generally befrom 5 to 45%, preferably from 10 to 30% of a synthetic anionic ornonanionic detergent; l5 to preferably from 25 to 45% of a water solubleinorganic builder or filler salt; and the balance of adju vantmaterials. As examples of the adjuvants may be mentioned coloringagents, pigments, perfumes, colloidal anti-redeposition agents,thickeners, gums, dispersing agents, hydrotropes, wetting agents,corrosion in hibitors, conditioning agents, desiccants, bactericides,fungicides, enzymes, solvents, bleaching agents, oxidizing agents,catalysts, reductants, or other suitable materials to impart specificproperties to the product.

The anionic synthetic organic detergents ar usually either sulfated orsulfonated compounds having lipophilic and hydrophilic portions thereon.They are generally used as water soluble salts, such as the alkalimetal, alkaline earth metal, ammonoum, alkylamine or alkanolamine salts.The sulfated or sulfonated materi' als are usually either higher alkylor higher alkyl aryl compounds, such as lauryl sulfate, tridecyl benzenesulfonate, palmityl sulfonate, or analogous phosphates or phosphonates.The alkyl groups are usually of 12 to 18 carbon atoms and the aryl groupwill ordinarily be benzene, although toluene and xylene coupounds mayalso be employed. The nonionic detergents are usually fairly long chainmaterials obtained by polymerization of iower alkylene oxides, such asethylene oxide or propylene oxide, and termination of the chain with ahydroxyl group. As examples thereof there may be mentioned the blockco-polymers of ethylene oxide and propylene oxide or polyoxyethyleneethanol, wherein the polymer is of 5 to 15 ethylene oxide groups. Alsoemployed are those nonionics wherein the polyoxy lower alkylene chain isjoined to an aryl or alkyl group, such as nonyl phenol polyoxyethyleneethanol and lauryl polyoxyethylene ethanol. Higher fatty esters andethers thereof are also useful. Among the inorganic builder and fillersalts are pentasodium tripolyphosphate, tetrasodium pyrophosphate,sodium sulphate, sodium carbonate, sodium bicarbonate, potassiumtripolyphosphate, potassium orthophosphate, magnesium pyrophosphate andvarious equivalent acidic salts, hydrates and derivatives thereof.

The following example illustrate preferred embodiments of the presentinvention, utilizing apparatuses substantially as shown in theaccompanying illustrations. IT is understood that the invention is notlimited to the illustrated examples or to the drawings. Obviously,equivalents may be substituted and various modifications may be madewithout departing from the priciples of the invention.

EXAMPLE l One hundred parts of borax pentahydrate, Na B- O .5H O, soldcommercially by American Potash Company as V Bor, are fed from a hopperinto a heated tower of the design illustrated in FIG. 1, at the rate of100 parts per minute. The particles being decrepitated in the tower areof sizes within the range of 16 mesh to 200 mesh, with about one-halfthe weight of particles passing a 60 mesh screen, and with about 2 /2%being finer than 200 mesh. The tower is at substantially atmosphericpressure and the internal temperature of the gas in the tower, heated bythe external heaters, is from 130 to 160C. The air flow is an unforcednatural venting flow upward at an average speed of 0.5 ft./second, withthe air serving as a purge to remove water vapor from the tower andalso, to an extent, helping to control the dwell time of the fallingborax particles in the tower. No blowers are employed. The tower, whosewalls are at a temperature of about 300C, heated by the gaseous productsof combustion of fuel oil in air, is of a diameter of about 2 feet and aheight of about feet, with the actual decrepitation zone height beingabout 6 feet. The dwell of the average particle of borax in thedecrepitation zone is about 3 seconds.

The borax pentahydrate particles, in falling through the tower ordecrepitation zone in an essentially free fall, are dehydrated andexpand, so that the particles removed at the base of the tower are in aparticle size range from to 100 mesh, mostly beng capable of passingthrough a 50 mesh screen. They are essentially anhydrous, although bylowering the temperature of the walls of the tower and decreasing dwelltime in the tower, particles of monohydrate or other hydrates lower thanthe pentahydrate may be produced, as may be mixtures thereof. Thedensity of the particles made is about 0.l3 g./cc., compared with thedensity of the particles charged, of 0.93 g./cc., measured as bulkdensity. The decrepitated particles are all larger than 200 mesh, andare more uniform in size.

The particles produced are more delicate than ordinary spray dried beadsbut are sufficiently strong to withstand breakage when processed inaccordance with the method of this invention. The particles dissolvereadily in water and the product is suitable for blending with otherdetergent ingredients in dry mixes, or it may be employed alone. Themethod described is economical and may be practiced in ordinary spraydrying or.

crystallizing towers, thereby avoiding the need for the construction ofspecial facilities. Furthermore, the process lends itself to use infactories where it is desired to use both anhydrous and hydrated formsof borax, either alone or in conjunction with the processing ofdetergent compositions.

EXAMPLE 2 Following essentially the same method as practiced in Example1, but with the modification that the decrepitation zone is part of aspray drying tower employed to dry detergent mixtures, a combination ofsprayed and decrepitated detergents is made. The apparatus employed isthat shown in FIG. 2. The tower is heated by the products of fuel oilcombustion in air, which raise the interior temperature of the tower to400"C., hot enough to spray dry the detergent composition charged, whichis a crutcher mix of 10% sodium lauryl benzene sulfonate, 18%pentasodium tripolyphosphate, 22% adjuvants, including hydrotrope,wetting agent, colloids, pigments, bactericides, and conditioningagents, and 50% water. One hundred parts per minute of such a crutchermix are sprayed into the upper portion of the tower at a pressure of 600lbs/sq. in. and a temperature of 60C. through spray nozzles that formparticles mostly within the 12 to 100 mesh size range. Simultaneouslywith the spraying of the crutcher mix, 8 parts of borax pentahydrate arefed to the decrepitation zone of the tower, below the point where thespray dried beads are essentially dry. The regulation of feed ratesresults in a product having about 19% organic detergent, 35%tripolyphosphate, 10% anhydrous borax and 3% water, the balance beingadjuvants.

Other than the internal temperature and the use of combustion gases asthe gas feed to the tower, other conditions mentioned in when l areemployed to give the desired decrepitated product. Of course, dwell inthe tower is decreased with the gas temperature is high so that theborax will not'be converted to a form that has little physical strength.To accomplish this, the point of addition of the borax may be lowered sothat it enters the tower through valve 75, when desired. Actually, thepoint of inlet of the borax will usually be near the bottom of thedrying zone and the four inlets illustrated are all close to the bottom,in actual practice.

EXAMPLE 3 The procedure of Example 2 is followed with the exception thatthe 8 parts of borax pentahydrate are replaced with 5 parts and 2 partssodium perborate, an unstable oxidizing agent. Both are admitted assolids, near the bottom of the tower, or the perborate is sprayed inthere as an aqueous solution-suspension. Particle sizes approximatethose given above and the resulting fortified oxidizing detergentcomposition is a good bleaching detergent.

Following the processes of either Example 2 or Example 3, when the weighbelt indicates that the density of the product is too high, anelectrical impulse actuates valve 87 to increase borax feed (since theborax has a lower density than that of the detergent particles alone),whereby average product density is increased. The opposite procedure isfollowed when the density becomes too low. Where borax-detergent ratiosare to be maintained constant, the electrical impulse from the weighbelt actuates valves 65, 67, 69 and to lower the effective point ofaddition of the borax and decrease average dwell time in the tower whendensity is too low and to raise the point of entry of the borax when thedensity exceeds that desired. This permits adjustment of the watercontent and the degree of expansion of the borax beads and adjusts theoverall density of the detergent particles containing borax particles.Of course, both adjustments of height of addition and amount of additionof borax may be used together and the other conditions of operation ofthe spray tower and the decrepitation zone may be modified to permit themaking of a product of the desired density.

What is claimed is:

1. A method for producing a non-stratifying, boraxcontaining detergentcomposition wherein the proportion of borax in the which comprisespassing particles is from Ill-50% of feed hydrated borax having aparticle size within the range of 20 to 200 mesh downwardly through ahot drying gas moving countercurrently at a speed of 0.05 to 5 ft./sec.in a drying zone defined by an enclosing wall, the temperature of saiddrying gas being from 120 to 600C, the pressure in said drying zoneranging from atmospheric to l m.m. of mercury vacuum, the dwell time ofsaid borax particles in the drying zone being from 0.1 to seconds sothat the temperature of the borax particles does not exceed 100C,whereby to produce a product borax particles having a moisture contentof l to 10% and a bulk density about 0.1 to 0.8 times the bulk densityof the feed borax particles, concurrently spraying into said drying zonea detergent slurry at a point above the point of introduction of thehydrated borax particles blending the spray dried particles of detergentcomposition with the particles of borax being decrepitated and removingthe mixed detergent borax composition from the dehydrating zone.

2. A method according to claim 1 wherein the removed detergent-boraxcomposition is tested for density and the ratio of borax hydrate todetergent mixture charged to the drying zone is changed to control thedensity of the detergent-borax composition being made.

3. A method according to claim 1 wherein the removed detergent-boraxcomposition is tested for density and the point or points ofintroduction of the borax hydrate into the drying zone are changed tocontrol the density of the borax particles produced and thereby controlthe density of the detergent-borax composition.

4. A method according to claim 2 wherein the means for testing densityis a weigh belt and the deflection of the belt actuates means for addingborax hydrate particles to the dehydrating zone when the density ishigher than desired and diminishes the feed rate of the borax hydratewhen the density is lower than desired.

5. A method according to claim 3 wherin the means for testing density isa weigh belt and the deflection of the belt actuates means for addingborax particles to the dehydrating zone at a relatively high level whenthe density is too high and of adding such particles at a relatively lowlevel when the density is too low.

6. A method to claim 1 wherein a detergent composition constituent thatis not stable to spray drying conditions is added to the decrepitationzone with the borax hydrate.

7. A method according to claim 6 wherein the unstable constituent issodium perborate.

1. A METHOD FOR PRODUCING A NON-STRATIFYING, BORAXCONTAINING DETERGENTCOMPOSITION WHEREIN THE PROPORTION OF BORAX IN THE WHICH COMPRISESPASSING PARTICLES IS FROM 10-50% OF FEED HYDRATED BORAX HAVING APARTICLE SIZE WITHIN THE RANGE OF 20 TO 200 MESH DOWNWARDLY THROUGH AHOT DRYING GAS MOVING COUNTERCURRENTLY AT A SPEED OF 0.05 TO 5 FT./SEC.IN A DRYING ZONE DEFINED BY AN ENCLOSING WALL, THE TEMPERATURE OF SAIDDRYING GAS BEING FROM 120* TO 600*C., THE PRESSURE IN SAID DRYING ZONERANGING FROM ATMOSPHERIC TO 1 M.M. OF MERCURY VACUUM, THE DWELL TIME OFSAID BORAX PARTICLES IN THE DRYING ZONE BEING FROM 0.1 TO 10 SECONDS SOTHAT THE TEMPERATURE OF THE BORAX PARTICLES DOES NOT EXCEED 100*C.,WHEREBY TO PRODUCE A PRODUCT BORAX PARTICLES HAVING A MOISTURE CONTENTOF 1 TO 10% AND A BULK DENSITY ABOUT 0.1 TO 0.8 TIMES THE BULK DENSITYOF THE FEED BORAX PARTICLES, CONCURRENTLY SPRAYING INTO SAID DRYING ZONEA DETERGENT SLURRY AT A POINT ABOVE THE POINT OF INTRODUCTION OF THEHYDRATED BORAX PARTICLES BLENDING THE SPRAY DRIED PARTICLES OF DETERGENTCOMPOSISITON WITH THE PARTI-
 2. A method according to claim 1 whereinthe removed detergent-borax composition is tested for density and theratio of borax hydrate to detergent mixute charged to the drying zone ischanged to control the density of the detergent-borax composition beingmade.
 3. A method according to claim 1 wherein the removeddetergent-borax composition is tested for density and the point orpoints of introduction of the borax hydrate into the drying zone arechanged to control the density of the borax particles produced andthereby control the density of the detergent-borax composition.
 4. Amethod according to claim 2 wherein the means for testing density is aweigh belt and the deflection of the belt actuates means for addingborax hydrate particles to the dehydrating zone when the density ishigher than desired and diminishes the feed rate of the borax hydratewhen the density is lower than desired.
 5. A method according to claim 3wherin the means for testing density is a weigh belt and the deflectionof the belt actuates means for adding borax particles to the dehydratingzone at a relatively high level when the density is too high and ofadding such particles at a relatively low level when the density is toolow.
 6. A method to claim 1 wherein a detergent composition constituentthat is not stable to spray drying conditions is added to thedecrepitation zone with the borax hydrate.
 7. A method according toclaim 6 wherein the unstable constituent is sodium perborate.